Vehicle windshield cleaning system

ABSTRACT

Apparatus for providing a heated cleaning fluid to a vehicle surface having an inlet port for receiving an amount of fluid; a housing bounding a reservoir in fluid communication with the inlet port; and an outlet port in fluid communication with the reservoir for dispensing an amount of heated fluid. A heater element heats fluid that passes from the inlet to the outlet port through the reservoir. A heat exchanger in thermal contact with the heater element for conveying heat to the fluid within the reservoir has a strut that divides fluid entering the housing through the inlet port into two flow paths and elongated fins that extend outwardly from the strut at transverse angles that bound fluid flow channels for fluid moving through said reservoir. A control circuit energizes the heater element with a voltage to heat the heating element and the fluid passing from the inlet to the outlet through the reservoir.

RELATE BACK

The present application is a divisional patent application claimingpriority to U.S. patent application Ser. No. 13/414,912, filed Mar. 8,2012 which is a divisional patent application claiming priority to U.S.patent application Ser. No. 12/393,111 entitled “Vehicle WindshieldCleaning System”, filed Feb. 26, 2009 which is a continuation in part ofapplication Ser. No. 11/928,738 filed Oct. 30, 2007 which claimspriority from provisional application Ser. No. 60/952,036, filed Jul.26, 2007 and is also a continuation in part of co-pending applicationSer. No. 11/341,116 filed Jan. 27, 2006 which is a continuation in partof application Ser. No. 10/894,266, filed Jul. 19, 2004 (claimingpriority from provisional application Ser. No. 60/551,571, filed on Mar.9, 2004), all of which are incorporated herein by reference and fromwhich priority is claimed.

FIELD OF THE INVENTION

The present invention concerns a windshield cleaning system, and moreparticularly to a windshield cleaning system that heats cleaning fluidapplied to the windshield.

BACKGROUND ART

U.S. Pat. No. 6,364,010 entitled “Device to Provide Heated Washer Fluid”to Richman et al. concerns an apparatus and method for improving thecleaning and deicing effectiveness of a washer fluid in a motor vehiclebefore spraying it against a windshield, headlamps, etc, and utilizesthe heat from the engine coolant to elevate the temperature of thewasher fluid. U.S. Pat. Nos. 5,957,384 and 6,032,324 also concernde-icing of a windshield.

SUMMARY OF THE INVENTION

The invention concerns apparatus and method for providing a large amountof heated cleaning fluid to a vehicle surface. An exemplary system hasan inlet port for receiving an amount of fluid; an outlet port fordispensing an amount of heated fluid; a heating element that heats upfluid passing from the inlet to the outlet; and a control circuit forenergizing the heating element with a voltage to heat the fluid passingfrom the inlet to the outlet.

In one exemplary embodiment, the system provides heated cleaning fluidto a vehicle surface and includes structure defining an inlet port forreceiving an amount of fluid, an outlet port in fluid communication witha reservoir for dispensing an amount of heated fluid.

These and other objects advantages and features of the invention willbecome better understood from the following detailed description of oneexemplary embodiment of the present invention which is described inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematic of a representative system for usewith the present invention;

FIG. 2 is an alternate block diagram schematic of a representativesystem for use with the present invention;

FIG. 3 is a schematic diagram of a drive circuit coupled to a fluidheating element that forms part of the FIG. 2 system;

FIGS. 4-7 are schematic depictions of control circuits for use with awasher control system constructed according to an alternative embodimentof the present invention;

FIG. 8 is a perspective view of a heating assembly coupled to a fluidpump;

FIG. 9 is a plan view of an exemplary heating canister constructed inaccordance with the invention;

FIG. 10 is a section view of a canister having two glow plugs and inletand outlet ports spaced to the side;

FIG. 10A is a view as seen from the line 10A-10A in FIG. 9;

FIGS. 11, 12, and 13 depict an alternate embodiment of a fluid heatingsystem;

FIGS. 14 and 15 illustrate operation of a check valve for use with theinvention;

FIGS. 16 and 17 are schematic diagrams of a representative system foruse with the present invention as shown FIGS. 9, 10 and 10A; and

FIG. 18 is a perspective view of a heater assembly employing a heat sinkand glow plug heating elements supported in a reservoir;

FIG. 19 is a side plan view of a housing supporting glow plugs and heatsink for heating fluid entering the housing;

FIG. 20 is a section view as seen from the plane 20-20 in FIG. 19;

FIG. 21 is a depiction of one housing portion of the FIG. 19 housingshowing mounting flanges;

FIG. 22 is a plan view of the reservoir with a cover removed to show theposition of an inlet and outlet;

FIG. 23 is an exploded perspective view of the heater assembly of FIG.18; and

FIG. 24 is perspective view looking into a heating reservoir.

EXEMPLARY EMBODIMENT FOR PRACTICING THE INVENTION

The drawings depict embodiments of the present invention that concern awasher control system 10 for use with a vehicle. In the disclosedembodiments of the invention, the control system 10 is used inconjunction with a windshield washer apparatus. The control system 10includes a control circuit 14 that includes an electronic output drivesignal circuit 20 and an input signal interpretation or conditioningcircuit 16.

The input signal interpretation circuit 16 electronically interfaceswith at least one temperature sensor 18. In one embodiment of theinvention, the temperature sensor provides signals related to thetemperature of washer fluid supplied to windshield spray nozzles on thevehicle. In one embodiment of the invention, the control system alsoincludes an electronic output circuit that drives an output powercontrol for at least one heating element that heats the windshieldwasher fluid. One exemplary control system could have both “high side”and “low side” type drives working together as illustrated in FIG. 2. Analternate control system is a “low side” type drive, meaning the moduleactivates and deactivates the heater element by controlling theelectrical circuit path to ground. Another alternate control systemcould have an output drive that is a “high side” type, meaning themodule activates and deactivates the heater element by controlling theelectrical circuit path to a power source. In accordance with anotheralternate control system, an electrical interface coupled to a vehicularcommunication bus allows the control system to be controlled by vehiclecommunications and makes data available to the vehicle for operation anddiagnostics of the control system.

The control circuit 14 includes a programmable controller ormicroprocessor 14 a that implements control algorithms for washer heatercontrol output functions in response to vehicle input signals. As seenin the functional schematic of FIG. 1, the control system 10 includes anelectronic output 12 from the control circuit 14 for providingcontrolled current to the heating element 30. Heating element 30 may becomposed of a single heating element or multiple heating elements. Byselecting heater current draw and power rating the heating time andtotal system current draw can be modified over a wide range of operatingparameters based on individual vehicle requirements, ie. electricalpower available. The control circuit 14 also includes an input signalinterpretation circuit 16, or interface, to monitor input signals from,as one example, the temperature sensor 18. The temperature sensor 18provides signals that allow for control of the amount of power deliveredto the heating element 30. The controller monitors inputs from a vehiclebattery 40 and vehicle ignition 42. It is understood that a separateignition input 42 may not be required if all power is obtained from thebattery input 40. In accordance with another alternate embodiment asillustrated in the functional schematic of FIG. 2, the controller alsomonitors a user input and drives a vehicle washer fluid pump 45 a (FIG.8) having a pump motor.

In one exemplary embodiment, the electronic output circuit 20 controlspower coupled to a heater element 30 (FIG. 1) that includes two glowplugs 30 a, 30 b (FIG. 10), or other heating element equivalents such asnichrome wire, ceramic heaters, or any metallic or non-metallic typeheater mounted in thermal contact with a heat exchanger 80 as shown inFIGS. 9 and 10. Fluid is routed past the heat exchanger 80 in thermalcontact with these elements by routing fluid into an inlet 32 andforcing the fluid out an outlet 34 having a check valve to prevent fluidleaving the outlet 34 from re-entering a fluid reservoir 103. Thecheckvalve could be positioned on the inlet 32. The inlet receiveswasher fluid from a fluid reservoir 35 (FIG. 8) of a motor vehicle andthe outlet 34 delivers heated washer fluid to nozzles 37 (FIG. 8)mounted to the vehicle which direct the washer fluid against the vehiclesurface, typically a windshield, headlamps etc. In the exemplaryembodiment the heating elements 30 a, 30 b are glow plugs. FIGS. 9 and10 depict an exemplary embodiment of a housing 41 that defines a fluidreservoir 103 that surrounds the heat sinks. The housing 41 isconstructed from plastic, or other material with favorable thermalcharacteristics.

The programmable controller 14 (FIG. 1) constructed in accordance withthe exemplary embodiment of the invention implements control algorithmsfor washer heater control output functions in response to vehicle inputsignals. As washer fluid temperature changes due to ambient temperaturechanges, battery voltage changes, and the like, the duration of appliedheat is increased or decreased in order to maintain a washer fluid at ornear a target temperature. Control of the heating may also includeredundant failsafe mechanisms such as a thermal fuse 524 (FIG. 9).

Controller Schematics

The block diagram shown in FIG. 1 and the more detailed schematic ofFIG. 4 depict operation of a control system 10 having externalelectrical connections, which include Battery 40, Ground 44, andIgnition 42. The system block diagram 111 shown in FIG. 2 shows furtherexternal electrical connections including a user operated Clean Switch113 and an output 115 to drive a vehicle washer pump motor. The Batteryinput connection 40 provides the voltage supply needed by the controlsystem 10. This connection allows the high current flow required by theheating element. The Ground connection 44 provides the current returnpath to the battery negative terminal. This ground connection allows thehigh current flow required by the heating element plus the requirementof the control system 10. An Ignition input 42 provides power to thecontroller. It is understood that separate ignition input 42 may not berequired if all power is obtained from battery input 40. The batteryvoltage is monitored by the controller 14 to determine if there issufficient voltage present to allow the control system to operate.

The input 102 from the temperature sensor 18 in physical contact withthe heat exchanger 80 is directly related to washer fluid temperature.Washer fluid temperature is monitored by using a temperature sensor suchas a thermistor, RTD, or the like. The washer fluid is monitorednon-invasively by attaching the temperature sensor to the heater.Alternatively, the fluid temperature could be monitored invasively byplacing a temperature sensor directly into the fluid through a threadedfitting or other suitable attachment method.

Operation

The controller receives a wake-up command signal from the Ignition input100 (FIG. 3). When the Ignition input is above a predetermined voltage,the controller 14 drives the heater element 30 if the following aretrue:

-   -   1. The ignition voltage is greater than a first predetermined        level and less than a second predetermined level.    -   2. The sensed Heater element temperature is less than a        predetermined level. Cleaning the windshield with warmed fluid        can be accomplished by the following:        -   a. Application of ignition 42 will cause the unit to heat            the volume of fluid. During the heating time an indicator            LED 119 flashes. Alternately, the LED could remain off until            the fluid has been heated at which time the LED will turn on            either 100% or flashing. The LED is shown as part of the            clean switch 113, but a skilled artisan could move the            indicator external to the switch.        -   b. During heating of the fluid if the clean switch 113 is            pressed, the LED will begin flashing to confirm the            operator's desire to use smart mode. If heating has already            completed and the indicator lamp is illuminated (not            flashing), momentarily activating the clean switch 113,            initiates a smart mode consisting of the energization of a            washer pump and wiper motor. During heating        -   c. Output 115 activates the washer pump 117 to dispense            fluid on the windshield. In the embodiment shown in FIG. 4,            an external controller 123 activates a wiper motor 121 in            response to a signal from the washer switch 113. One skilled            in the art could have the same controller 14 activate the            wiper motor 121 and the washer pump 117.        -   d. Hot fluid will be sprayed on the windshield and the            windshield wipers will cycle automatically, when the hot            fluid reduces to a predetermined temperature or time, output            115 deactivates, thus completing the smart mode and washer            spray/wiper cycling will halt. Momentarily pressing clean            switch 113 during the smart mode will cancel the operation.            The cleaning switch can be configured to heat fluid to a            predetermined temperature (or time) and dispense and reheat            and dispense fluid multiple times.    -   2. With ignition 42 applied and when indicator 119 is        illuminated (not flashing) indicating warm fluid is available,        the activation of the existing vehicle wash switch will dispense        fluid for as long as the switch is closed for on-demand        cleaning.    -   3. The activation of the existing vehicle wash switch will        dispense fluid for as long as the switch is closed for on-demand        cleaning regardless of fluid temperature.

An output driver 20 depicted in FIG. 1 and FIG. 2 applies power to theheater after starting the heating cycle. The output driver will thenbegin applying power to the heater to maintain the temperature of thefluid. A fuse 55 is located between the battery connection and theheater element external to the housing 50 in the illustrated embodimentas shown in FIG. 8. An alternative embodiment could have the fuse 55internal to the housing as shown in FIG. 1. In the exemplary embodimentof the invention, the desired heater temperature is predetermined to bein a range between 120 and 150 degrees Fahrenheit. Placing thetemperature sensor 18 in physical contact with the heating element andmaintaining the heater temperature at a temperature at or below 150degrees Fahrenheit prevents the heating element from heating thecleaning fluid to an undesirable temperature, such as boiling. Thishelps prevent the formation of mineral deposits that could potentiallyclog the nozzle 37 (FIG. 8). As depicted in FIG. 9 if the temperaturesensor 18 is not mounted directly on the heating element, but is ratherlocated in the fluid reservoir 103, only an approximate, latentmeasurement of the heating element temperature is sensed. This wouldallow the heat exchanger 80 to heat to a temperature that is hotter thanthe desired fluid temperature in reservoir 103 and potentially cause theformation of nozzle clogging mineral deposits. The output driver 20(FIGS. 1, 2) will remain active as long as the ignition voltage is abovea predetermined voltage and the heater temperature is below the desiredheater temperature as determined by the temperature sensor 18. When theignition 42 is turned off, the controller is deactivated.

FIG. 3 depicts one implementation of the output circuit 20. A heaterconnection 60 is shown in the upper right hand portion of the FIG. 3depiction. This connection is grounded by means of initiating conductionof two power Field Effect Transistors (FET) 110, 112 which provide acurrent path to ground from the heater connection 60 to the groundconnection 44 through a pair of reverse polarity protection FETtransistors 114, 116. The two transistors 110, 112 are turned on orrendered conductive by means of a pre-drive transistor 120 that iscoupled to an output 122 from the microprocessor controller 14 a (FIG.1). First consider a high signal from the controller 14 a at this output122. This turns on transistor 120 that pulls an input 124 of a totempole transistor combination 126 low. This signal turns on a lower of thetwo transistors of the totem pole combination to send an activationsignal that turns off the two FETs 110, 112.

When the controller provides a low output from the controller 14 a atthe output 122, the transistor 120 turns off and pulls an input 124 to atotem pole transistor combination 126 high. This signal turns on anuppermost of the two transistors of the totem pole combination to sendan activation signal that turns on the two FETs 110, 112.

In the illustrated embodiment, a comparator 140 monitors current throughthe transistors 114, 116 (and by inference the transistors 110,112) anddeactivates the transistors in the event too high a current is sensed. Afive volt signal that is supplied at an input 142 from a power supply(FIG. 1) provides a reference input 144 to the comparator 140. When thenon-reference input exceeds the reference input due to a rise in thecurrent through the transistors 110, 112 (and associated rise in thevoltage across the transistors 114, 116) the output 146 of thecomparator goes low and removes the input from the gate of the FETs 110,112 that causes them to conduct. This low signal at the output 146 isalso coupled to the controller so that the controller can respond to theover current condition.

In accordance with the exemplary embodiment of the invention athermistor temperature sensor 18 is also coupled to the controller. Asignal at a junction between the temperature sensor 18 and a resistorcoupled to the five volt input 142 generates a signal at an input 150related to the temperature of the heater element 30 (FIG. 1).

Referring to FIG. 9, in one embodiment, the control circuit 14 ismounted to a printed circuit board 92 supported by a housing 41. As seenin FIG. 3, a connector 60 is a bent metallic member that attaches to theheating element 30 in the vicinity of the printed circuit board 92 andis in physical contact with the circuit components on the printedcircuit board. The connector 60 thereby not only acts as a path toground for current passing through the heating element 30 but acts as aheat sink that transmits heat away from the printed circuit board.

The exemplary control circuit includes a microcontroller as shown inFIG. 1 running at an internal clock frequency of 4.0 Megahertz. In theexemplary embodiment, the microcontroller 14 a selectively energizes theheating element 30 based on a voltage applied to the control circuit.This voltage may be the battery voltage 40 and/or the ignition voltage42. When the ignition input voltage is applied, the control circuit willpower up, come out of reset, and wait for a start delay time imposed bythe controller to allow the vehicle's electrical system to becomestable. After this start delay, the control circuit monitors theignition voltage to determine if the ignition is above a minimum enablevoltage. A temperature signal from the sensor 18 is also monitored tosee if the temperature of the fluid is below a set point temperature. Anoutput drive feedback signal is also monitored to ensure that the outputis in the correct state. If all conditions are such that the output canbe enabled, the output 122 (FIG. 3) to the transistor 120 is pulled low.This initiates fluid heating. Initially, the output drive is on 100% fora maximum on time or until the feedback temperature reading approaches aset point temperature. In one embodiment, a preset maximum on time isempirically derived to stay below the boiling point of the cleaningfluid. Subsequently the control will read the heating element 30temperature and make a determination if power should be reapplied. Ifthe sensed temperature is below the desired setpoint, the output will bere-enabled at a variable duty cycle so that the heating element 30 isheated to the setpoint goal temperature as quickly as possible withoutexceeding a maximum allowable overshoot temperature.

Normal operation consists of maintaining the fluid temperature at thedesired setpoint temperature by varying the duty cycle at which voltageis applied across the heating element 30. The output duty cycle changesbased on how far the sensed temperature is below the set pointtemperature.

In the event of excessive current flow through the power drive 20, theoutput 12 will automatically be disabled. In this event the signal atthe output 146 from the comparator 140 (FIG. 3) will go low. When thisoccurs the controller 14 a disables the output to the transistor 120 fora period of time equal to an output retry rate programmed into thecontroller 14 a. If the fault condition is removed, normal operation ofthe temperature set point control is re-instituted. An alternateembodiment could have the current sense capability implemented by thecomparator 140 omitted.

In the event the operating voltage from the battery (and ignition) istoo high or too low (≧16.5 and ≦8 volts respectively) the controller 14a disables the output 12 for a timeout period. After the timeout period,if voltage conditions are within normal parameters, the controller againenables the output. It is understood that the operating voltage rangecan be set to whatever voltages are required for a particularapplication. The exemplary system also incorporates a soft turn-on andturn-off of the heating element. The soft turn-on and turn-off isaccomplished by a slow ramp up or down of the output 20 that drives theheating element. The ramping of power reduces the amount of flickeringthat can be observed from the vehicle headlights. It is recognized thatthe FET drivers could be run linearly to accomplish the soft turn-on andturn-off of the heating element. It is also recognized that the FETdrivers could be run linearly to regulate the temperature of the heatingelement. It is further recognized that if the FET drivers are runlinearly they will produce quantities of heat that will aid in theheating of fluid in the system.

FIGS. 5 and 6 illustrate an embodiment of a washer control system 10that is different from that described previously due to the replacementof control circuit 14 with a thermal fuse device 524 and a bi-metaldevice 525. FIG. 5 is a schematic depiction of such a control circuit.The thermal fuse 524 prevents the washer control system 10 fromoverheating, while the bi-metal device 525 regulates heating duringoperation. The bi-metal device could control a relay 612 (see controlcircuit schematic of FIG. 6) that supplies power to the heating element.In addition, at least one temperature sensor could be used inconjunction with a reference to control a relay that supplies power tothe heating element.

In FIG. 7, the heater 30 is energized with battery voltage by a relay632 that is activated by ignition of the vehicle. A thermal fuse 637 isin series with the relay coil and is in proximity to the heater 30. Ifthe heater becomes too hot, the thermal fuse 637 will open and voltageis removed from the heater. The control circuit 14 shown in FIG. 1provides a digital signal to a heater energization circuit 630 shown inFIG. 7. A digital signal 635 from the controller is converted to ananalog voltage by a converter circuit 638. The converted voltage isprovided to a FET 645 as a gate voltage. The gate voltage varies betweenzero to a FET saturation voltage. The FET 645 is part of a current pathfor the heater 30 and dissipates an amount of heat that is proportionalto the driving voltage that is supplied to it. Since battery voltage ismonitored, and the resistance of the heater is known, current flowingthrough the heater can be calculated by the control circuit 14 to setand regulate the gate voltage. By controlling the relative amounts ofpower dissipated in the FET and heater, the control circuit can applyvarying amounts of current to maintain a desired fluid temperature. Bycontrolling the rate of rise and fall a soft turn an/off can beachieved.

FIGS. 9 and 10A illustrate an exemplary fluid heating assembly thatprovides a heated cleaning fluid to a vehicle surface. A plastic housing41 defines an interior elongated reservoir 103 and has an inlet port 32on one side of the housing for routing fluid into the reservoir from anexternal source. A connector C extends from a bottom 41 b of the housing41 when the housing is mounted within the engine compartment of a motorvehicle. The housing further has an outlet port 34 in fluidcommunication with the reservoir 103 for dispensing an amount of heatedfluid to a nozzle for spraying heated fluid from the reservoir onto asurface such as a windshield. The port 32 is generally circular in crosssection to mate with a hose coupled to a source of fluid. The port 32opens outwardly to a region having a greater cross section than the port32 which is bounded by four generally orthogonal walls to define anentryway 33 a for fluid to flow through on its way to contacting analuminum heater exchanger 80 positioned to the side of the entryway 33a.

The aluminum heat exchanger 80 has struts 85 of a length to extend fromone end wall 103 a to the other end wall 103 b of the reservoir and fitswithin and is supported by the plastic housing in a position that is atleast partially covered by fluid within the reservoir 103. First andsecond transversely spaced generally circular hub segments 82 arecoupled together by an intermediate bridging segment that supports asensor 18 and the thermal fuse device 524 in passages 83 a, 83 b thatextend completely through the heat exchanger. Each hub supports multiplefins 84 that extend outwardly from its associated hub and have a width Wthe same as the struts 85 to increase the surface area of the heatexchanger and promote heat transfer to the fluid in the reservoir. Theheat exchanger 80 may also be made out of other thermally conductivematerials such as copper. The heat exchanger is coated to preventoxidation or reaction with fluids. In the preferred embodiment it is aPTFE penetrated hardcoat anodization.

First and second glow plug heater elements include first and second glowplugs 30 a, 30 b for heating fluid that passes from the inlet 32 to theoutlet port 34 through the reservoir 103 in contact with the heatexchanger 80. The glow plug heater elements axially extend into the hubsof the heat exchanger so that heat emitting surfaces of the glow plugs(NSN: 2920-01-188-3863) are bonded to interior curved surfaces of thehubs by a thermally conductive material to transmit heat to the heatexchanger. The glow plug heating elements are coupled at one end withgenerally conductive connector plates 96 for routing energizing signalsto the glow plugs. Inside the reservoir, the heat exchanger hubs buttagainst shoulders 97 which extend outwardly a slightly greater amountthan the outer diameter of the heat conveying surface of the glow plugsto maintain a gap G between an edge of the heat exchanger fins andstruts and allows fluid to flow around a wall or barrier 86 whichextends to an edge 85 a of the strut from a wall 41 a of the housing andthat roughly divides the reservoir into two halves.

The combination of the interior reservoir 103 of plastic housing 41 andheat exchanger 80 with struts 85 and multiple fins 84 form a fluid pathfrom inlet port 32 to outlet port 34. The fluid path is formed by thecombination of the wall 86 that is generally centered in the reservoir103 and struts 85 and fins 84. As fluid enters reservoir 103 the fluidstream is divided into two halves by the strut 85. Each of the two fluidstreams flows through the reservoir in the direction of the arrows 87along respective sides of the heat exchanger 80 in an essentiallyparallel path until the two streams combine to flow beneath the wall 86,then again separate into two portions and flow in the direction of thearrows 88 to arrive at the region 33 b near the outlet port 34 where thetwo fluid streams are combined into a single stream. In the embodimentshown in FIG. 9 fluid exits the housing through an exit region 33 b alsohaving four walls through which fluid flows on its way to the circularlyshaped exit port 34.

Experience shows that thermal transfer from the center glow plug hubs isadequate if fluid flow is symmetrical about the hub center line (evenflow past the fins). The fluid close to the center of the heat exchangerhas a fairly short path from inlet to outlet. This does not give asignificant amount of time to have the fluid absorb the full amount ofheat available. FIG. 10 shows inlet and outlet ports moved to theoutside ends of the reservoir. This reduces some of the effectiveness ofheat transfer from the heat sink but it allows the fluid to stay in thereservoir for a longer time thus allowing more heat transfer to takeplace.

FIGS. 18-24 show a housing wherein fluid enters an inlet and follows aserpentine or back and forth path while extracting heat from an aluminumheat exchanger 280. The fluid enters the housing 241 through the inletport 232 and flows in the direction of an arrow 250 along the respectivesides of the heat exchanger 280 eventually reaching outlet port 234.Fins and housing details of a part 241 a of the housing that bounds areservoir 303 force the fluid to flow along one or the other side of astrut 285 a in two fluid streams. FIG. 18 depicts fluid flow on one sideof the strut 285 a as it flows in a serpentine pattern designated witharrows 310 first flowing along and around a fin 284 a and then along andaround the next fin 284 b. Once the fluid has flowed around the fourfins 284 a-d attached to the first generally circular hub segment 282 ait is forced over a wall feature 286 that is part of plastic housingpart 241 a and defines in part the reservoir 303. The fluid thencontinues transversing in a serpentine pattern along and around the nextfour fins 284 e-h that are attached to the second generally circular hubsegment 282 b. The two fluid streams on opposite sides of the housingcome to a second strut 285 b and then combine as the streams arrive atoutlet port 234.

Some benefits of the fluid path technique shown in FIGS. 18-24 are largeheated surface area to fluid volume ratio, extending duration of fluidto heat exchanger contact time, reduction of mixing of cold fluid withheated fluid, and lower flow restriction from inlet to outlet.

In the disclosed embodiment, the fins 284 a-h and struts 285 a,b as wellas the hub segments 282 a,b of heat exchanger 280 provide a large heatedsurface area of approximately 129 cm² and have a width of 35 mm. With afluid volume of approximately 40 ml a high surface area to fluid volumeratio greater than 2.5:1 of surface area to volume results whichprovides for rapid heating of fluid and efficient transfer of heat fromheating elements 230 supported within through passages 281 in the spacedapart heat exchanger hubs 282 a, 282 b. The serpentine path ofapproximately 356 mm causes the fluid to remain in contact with the heatexchanger 80 for a longer duration of time. Without the serpentine path,the fluid would only travel approximately 76 mm from inlet to outlet notallowing adequate time to take full advantage of the transfer heat fromheat exchanger 280. The serpentine fluid path also provides for betterseparation of cold inlet fluid from fluid that is heating or that hasalready been heated.

The heat exchanger fins 284 mate with corresponding lands or raisedportions that extend inwardly from interior walls of the housing. Thus,for example the fin 284 a at the end of the housing nearest the inletport contacts a land 329 which prevents fluid from entering thereservoir and flowing at right angles away from the inlet to the outlet.The sectioned perspective view of FIG. 18 illustrates other lands322-329 engaging ends of the fins of the heat exchanger. An intermediateor mid section 285 c of the strut engages additional lands 330, 332 ofthe housing that block passage of the fluid from one side of the strutto the other as the fluid flows through the reservoir. As seen in theview of FIG. 22 the lands are slightly thicker than the fins. The finsare angled away from the hubs to slip between bounding walls that defineslots 340 in the housing 241 a into which the fins slip duringfabrication.

The fins 284 provide a buffer against cold fluid readily mixing withpreviously heated fluid by forcing fluid to traverse the heat exchanger280 in a series fashion, fin by fin, section by section. This allowsfluid that has already been heated to be dispensed from the outlet port234 with minimal impact from cold fluid coming from the inlet port 232.Fluid travels along each side of heat exchanger 80 with up and downdirection changes. With parallel paths along both sides of the heatexchanger 280 a lower flow restriction is realized than the equivalentpath of serpentine back and forth direction changes with no parallelpath. This yields a lower flow restriction from inlet to outlet andprovides for more efficient spraying of fluid.

Glow plug heaters 230 fit into the passageways 281 bounded by the spacedapart hubs. Turning to FIG. 23, one sees two elastomeric seals 350, 352are inserted into the housing 241 a. A first seal 350 has a center boss354 and two side lobes 356, 358. The second seal 352 defines traces 360that mimic the orientation of the fins of the heat exchanger. Duringfabrication, the boss of the seal 350 is inserted into a centerpassageway before a temperature sensor (part number KC103G4K from USsensors) and thermal fuse (Part no. N6F from Tamura) 362, 364 are pottedwithin a throughpassage of the heat exchanger in thermal contact withthe interior walls of the throughpassage 366. The glow plugs 230 extendthrough openings 368 in a cover 370 that mates with the housing along anouter edge of the seal 352. The glow plugs are also potted within thepassageways extending through the hubs of the heat exchanger to assuregood thermal contact between glow plugs and the heat exchanger. Duringfabrication of the assembly, the heat sink and seal are inserted intothe reservoir by slipping the fins into the slots 340. The seal glowplugs and electrical conductors 372 for the temperature sensor 364 andthermal fuse 362 extend through the seal 352 and cover for externalconnection to a controller mounted on a circuit board in the housingportion 241 b. Connectors 374 engage threaded studs 376 to compress theseals 350, 352 and maintain a serpentine flow path of fluid entering theinlet 232. The two parts 241 a, 241 b of the housing mate along anangled edge of each housing. A ground connector 380 having a studreceiver type engagement with the glow plugs 230 is slipped over theglow plugs after the cover 370 is attached. Preferred glow plugs arepart number NSN: 2920-01-188-3863 commercially available from WAP, Inc.The preferred potting material for the ends of the glow plugs is ArcticSilver 5 commercially available from Arctic Silver Incorporated and thesensor and thermal fuse is EP1200 commercially available from Resin Lab.

A control circuit supported by a printed circuit board 92 supported bythe housing energizes the glow plugs with a voltage and thereby heatsfluid passing from the inlet to the outlet through the reservoir. Aplastic wall member 94 supported within the housing and has openings foraccommodating corresponding first and second glow plugs. A seal 95contacts the wall member and confines fluid to the reservoir bypreventing fluid from leaking outward from the reservoir past the wallmember. Air pockets 90 formed in the housing 41 surround the heatexchanger and provide insulation between the heat exchanger an theregion outside the housing. These pockets also serve as freezeprotection in the event water is frozen in the device. These airchambers allow the reservoir to expand with the freezing water. Foroptimal protection these chambers may be filled with a compressiblematerial to control the freeze expansion performance. The air pockets 90may be positioned to cover only a portion of the housing 41. Connectorsroute battery, ground and control signals to the control circuit mountedto the printed circuit board.

As depicted in FIGS. 14 and 15 the outlet 34 is defined by an end cap 91and flexible membrane 97 coupled to the housing 41. The end cap includesa center throughpassage 99 that allows fluid to flow out the outlet tothe nozzles. As fluid is forced through the reservoir, an elastomericmembrane 97 is forced against radially extending slots 98 which openinto a central passageway 99. Once the pressure is removed from thereservoir by deactivating the washer pump the membrane 97 moves from theposition shown in FIG. 14 to cover a narrow throughpassageway 105 toprevent fluid from flowing back into the reservoir from the nozzles.

FIGS. 12-13 show the system with a cover component 676 removed. In thisembodiment, control system 10 (FIG. 11) receives fluid through an inletport 681 that then enters into a heatsink 674. A previously describedpower FET component is electrically and mechanically attached to printedcircuit board (PCB) 675, using well known methods, and is joined withheatsink 674 by means of a threaded fastener or the like. The heatsink674 is preferably made from copper, or alloy materials such as aluminumthat are similarly effective in thermal transfer. The heatsink 674 isconfigured to contain a small volume of fluid, preferably situateddirectly opposite the flat mounting surface of a power FET, ideally forthe purpose of cooling power FET during system operation. Conversely,heat transferring from power FET 514 through the heatsink 674 serves toheat the fluid in the reservoir area, adding to the performance ofcontrol system 10.

A heatsink 674 also provides electrical connection between the PCB 675and a first heater coil 671 such as a coil that is depicted in U.S. Pat.No. 6,902,118 which is incorporated herein by reference. Fluid passesfrom heatsink 674 into first heater coil 671 through aperture 677,through temperature sensor fitting 678 and into second heater coil 672.Fluid dispenses into check valve block 680 through an entryway 679 andexits control system 10 by means of outlet port 673. A check valve block680 also provides electrical connection between PCB 675 and secondheater coil 672, and is preferably made from copper, or any alloymaterial capable of withstanding long term exposure to typical fluidsused in vehicle washer systems. The assembly as described is preferablyattached to base component 682 and enclosed in the cover 676 (FIG. 11),which are preferably molded from plastic material such as 30% glassreinforced polyester, such as that made by GE Plastics under the tradename Valox®. There are many other suitable materials available capableof withstanding the environment and conditions typical of those under avehicle engine compartment. Power is supplied to this embodiment ofcontrol system 10 by means of a connector assembly 683, while input andoutput commands are administered by means of a connector assembly 684.Similar connector assemblies are used in the FIGS. 9 and 10 embodimentof the control.

While the invention has been described with a degree of particularity,it is the intent that the invention includes all modifications andalterations from the disclosed design falling within the spirit or scopeof the appended claims.

The invention claimed is:
 1. A fluid heating assembly for providing aheated cleaning fluid to a vehicle surface comprising: a) a housingextending in a first direction defining two interior chambers spacedfrom each other in a second direction perpendicular to the firstdirection in a side-by-side configuration by a separating wall extendingin the first direction, said housing including an inlet port in fluidcommunication with one of said interior chambers defining a firstchamber for receiving and heating fluid from an external source; saidhousing further defining an outlet port in fluid communication with theone of said interior chambers for dispensing an amount of heated fluidto a nozzle for spraying heated fluid onto a surface wherein theseparating wall comprises a removable cover which at least partiallybounds the first chamber and separates said interior chambers,preventing fluid from leaking out of the first chamber into a secondchamber of said interior chambers containing electronics; b) a heatingelement disposed in the first chamber for heating fluid that passes fromthe inlet port to the outlet port through the first chamber; c) a heatexchanger supported by said housing in a position that is at leastpartially covered by fluid within the first chamber and coupled to saidheating element so that heat emitting surfaces of said heating elementengage and transmit heat to said heat exchanger; and d) a controlcircuit supported by a printed circuit board within the second chamberfor energizing said heating element with a voltage and thereby heatfluid passing from the inlet port to the outlet port through the firstchamber.
 2. The apparatus of claim 1 additionally comprising a flexibleseal interposed between the separating wall and the first chamber toinhibit leaking of fluid from the first chamber.
 3. The apparatus ofclaim 1 wherein the separating wall forms a boundary for each of thefirst and the second chambers.
 4. The apparatus of claim 1 wherein thecontrol circuit comprises an electrical interface for communicating witha motor vehicle communications bus to communicate data to other vehiclecomponents coupled to the communications bus.
 5. A method of providing aheated cleaning fluid to a vehicle surface comprising: a) providing ahousing extending in a first direction defining two interior chambersspaced from each other in a second direction perpendicular to the firstdirection in a side-by-side configuration; b) providing an inlet fluidpath in fluid communication with one of the interior chambers defining afirst chamber for receiving and heating fluid from an external source;c) providing an outlet fluid path in fluid communication with the one ofthe interior chambers for dispensing an amount of heated fluid to anozzle for spraying heated fluid onto a surface; d) separating the firstchamber from a second chamber of the interior chambers with a commonbounding wall that comprises a removable cover which at least partiallybounds the first chamber and extends in the first direction andseparates the first chamber and the second chamber in the side-by-sideconfiguration and prevents fluid from leaking from the first chamberinto the second chamber; e) mounting a heater and a heat exchanger inthe first chamber in heat transfer relation to each other for heatingfluid that passes through the first chamber; f) mounting a controlcircuit supported by a printed circuit board within the second chamberfor energizing the heater with a voltage and thereby heat fluid passingthrough the first chamber; and g) causing fluid to flow through thefirst chamber while energizing the heater to heat the fluid within thefirst chamber.
 6. The method of claim 5 wherein the heater and heatexchanger are mounted within the first chamber.
 7. The method of claim 6wherein the removable cover is removed during placement of the heatexchanger within the first chamber.
 8. The method of claim 5additionally comprising sealing a region of the wall in the firstchamber to inhibit seepage of fluid from the first chamber.
 9. Themethod of claim 5 additionally comprising coupling the control circuitto a motor vehicle communications bus for communicating data to othervehicle components coupled to the motor vehicle communications bus. 10.A fluid heating assembly for providing a heated cleaning fluid to avehicle surface comprising: a) a housing extending in a first directiondefining two interior chambers spaced from each other in a seconddirection perpendicular to the first direction in a side-by-sideconfiguration by a separating wall extending in the first direction,said housing including an inlet port in fluid communication with a firstchamber of said interior chambers for receiving and heating fluid froman external source; said housing further defining an outlet port influid communication with the first chamber for dispensing an amount ofheated fluid to a nozzle for spraying heated fluid onto a surfacewherein the separating wall comprises a removable cover which at leastpartially bounds the first chamber and separates the chambers in theside-by-side configuration, preventing fluid from leaking out of thefirst chamber into a second chamber of said interior chambers containingelectronics; b) a power source for heating fluid that passes from theinlet port to the outlet port through said first chamber; c) a heatexchanger supported by said housing in a position that is at leastpartially covered by fluid within the first chamber and including aheating element coupled to the power source so that heat emittingsurfaces of said heat exchanger transmit heat to the fluid within thefirst chamber; and d) a control circuit supported by a printed circuitboard within the second chamber for energizing said heating element ofsaid heat exchanger with a voltage from the power source and therebyheat fluid passing from the inlet port to the outlet port through thefirst chamber.
 11. The fluid heating assembly of claim 1 wherein saidcontrol circuit comprises a thermal fuse to render the heating elementinoperable if a temperature threshold is exceeded.
 12. The fluid heatingassembly of claim 11 wherein the thermal fuse electrically connected toa relay coil to render the relay coil inoperable if the temperaturethreshold is exceeded.
 13. The fluid heating assembly of claim 1 whereinsaid control circuit comprises a thermal sensor in direct thermalcommunication with the heating element.
 14. The method of claim 5wherein the control circuit comprises a thermal fuse to render theheater inoperable if a temperature threshold is exceeded.
 15. The methodof claim 14 wherein the thermal fuse is electrically connected to arelay coil to render the relay coil inoperable if the temperaturethreshold is exceeded.
 16. The method of claim 14 wherein the controlcircuit comprises a thermal sensor in direct thermal communication witha heating element of the heater.
 17. A fluid heating assembly forproviding a heated cleaning fluid to a vehicle surface comprising: a) ahousing extending in a first direction defining two interior chambersspaced from each other in a second direction perpendicular to the firstdirection in a side-by-side configuration by a separating wall extendingin the first direction, said housing including an inlet port in fluidcommunication with one of said interior chambers defining a firstchamber for receiving and heating fluid from an external source; saidhousing further defining an outlet port in fluid communication with theone of said interior chambers for dispensing an amount of heated fluidto a nozzle for spraying heated fluid onto a surface wherein theseparating wall comprises a removable cover which at least partiallybounds the first chamber and separates said interior chambers,preventing fluid from leaking out of the first chamber into a secondchamber of said interior chambers; and b) a heat exchanger supported bysaid housing in a position that is at least partially covered by fluidwithin the first chamber so that heat emitting surfaces of said heatexchanger transmit heat.
 18. A method of providing a heated cleaningfluid to a vehicle surface comprising: a) providing a housing extendingin a first direction defining two interior chambers spaced from eachother in a second direction perpendicular to the first direction in aside-by-side configuration; b) providing an inlet fluid path in fluidcommunication with one of the interior chambers defining a first chamberfor receiving and heating fluid from an external source; c) providing anoutlet fluid path in fluid communication with the one of the interiorchambers for dispensing an amount of heated fluid to a nozzle forspraying heated fluid onto a surface; d) separating the first chamberfrom a second chamber of the interior chambers with a common boundingwall that comprises a removable cover which at least partially boundsthe first chamber and extends in the first direction and separates thefirst chamber and the second chamber in the side-by-side configurationand prevents fluid from leaking from the first chamber into the secondchamber; e) mounting a heat exchanger in the first chamber for heatingfluid that passes through the first chamber.
 19. A fluid heatingassembly for providing a heated cleaning fluid to a vehicle surfacecomprising: a) a housing extending in a first direction defining twointerior chambers spaced from each other in a second directionperpendicular to the first direction in a side-by-side configuration bya separating wall extending in the first direction, said housingincluding an inlet port in fluid communication with a first chamber ofsaid interior chambers for receiving and heating fluid from an externalsource; said housing further defining an outlet port in fluidcommunication with the first chamber for dispensing an amount of heatedfluid to a nozzle for spraying heated fluid onto a surface wherein theseparating wall comprises a removable cover which at least partiallybounds the first chamber and separates the chambers in the side-by-sideconfiguration, preventing fluid from leaking out of the first chamberinto a second-chamber of said interior chambers; and b) a heat exchangersupported by said housing in a position that is at least partiallycovered by fluid within the first chamber so that heat emitting surfacesof said heat exchanger transmit heat to the fluid within the firstchamber.